Alkylation process



Nov. 25, 1947. J. E. PENICK ALKYLA'I'ION PRbcEss Filed Nov. 4, 1944llllllll .llll'll .585 E ww Joe E. Pem'ck IN VENTOR WRQQKQQQQ AGENTPatented Nov. 25, 1947 r UNITED STATES PATENT OFFICE 1 2,431,500 Joe E.Penickt nansf zlf fii by mesne enta, to Socony-Nacuum Oil Company,Incorporated, New York, N. Y., a corporation of New York ApplicationNovember 4, 1944, Serial No. 561,889

4 Claims. (01. 260-683.4)

This invention relates to the production of higher boiling hydrocarbonsfrom lower boiling hydrocarbons in the presence of catalytic agents andrelates more particularly to the alkylation of isoparafiins with oleflnsin the presence of acid catalysts.

As is well ,known, hydrocarbon products may be produced by alkylationreactions involving the combination or'condensation of two dissimilarhydrocarbon reactants in the presence of suitable catalytic agents.While various types of alkylate products may be obtained by employingvarious types of reactants, the alkylation of low boiling isoparamnssuch as isobutane and isopentane with low boiling olefins such asethylene, propylene, the isomeric butenes, and the isomeric pentenes,for the production of aviation fuels and high grade motor fuels hasbecome of particular importance. Sulfuric acid has been employed as acatalyst in isoparafin-olefln alkylation and more recently liquidhydrogen fluoride has found favor as a catalyst. The alkylation ofisobutane with butenes is representative of these reactions and has beencommonly carried out by feeding isobutane and butene feed stocks in theliquid state along with liquid hydrogen fluoride to a multi-passalkylation reactor such as the reaction loop type reactor, wherein thehydrocarbons and catalyst are vigorously agitated and continuouslycirculated within a closed circuit. The reaction is exothermic andtemperature control is important to prevent localized 01' generaloverheating of the reaction mixture with consequent deleterious efiecton the yield and quality of the alkylate product as a result of sidereactions occurring at elevated temperatures. Temperature control isobtained by means of internal heat exchangers over-which the reactionmixture passes proper control of the reaction temperature and because ofthe belief that very high ratios of saturated hydrocarbons tounsaturated hydrocarbons were essential to prevent olefin polymerizationtherefore making it desirable to recirculate the saturated hydrocarbonproducts.

It is an object of this invention to provide an improved alkylationprocess. It is another object of this invention to provide a process forthe alkylation of isoparaflins with olefins in singlepass reactors. Itis another object of this invention to provide a method for controllingthe temperature of isoparafin-oleiin alkylation mixtures in single-passreactors. Further objects and advantages of the invention will becomeapparent from the following description thereof.

In accordance with the invention, the above objects are achieved by aprocess which involves or by passing a portion of the continuouslycirculating mixture through an external heat exchanger. A portion of thecirculating reaction mixture is continuously withdrawn from the reactorand the acid allowed to settle therefrom, after which the hydrocarbonproduct is treated for removal of excess isobutane reactant and re--moval of normal butane and any lighter hydrocarbons which may bepresent, the acid and the isobutane being recycled to the reactor. Ithas been proposed to carry out the alkylation reaction in single passreactors, i. e., reactors in which the reaction mixture is notcontinuously circulated, but such reactors have not been extensivelyused, despite the fact that they possess advantages not possessed bymulti-pa'ss reactors, primarily because of the difficulty of obtainingfeeding to a single-pass reaction zone a, volumeratio of acid catalystto total hydrocarbons of at least three to one, separating the acidcatalyst from the reactor efiluent, recycling at least a portion of theseparated acid, and cooling at least a portion of the recycled acid tomaintain the temperature of the reaction mixture ata predeterminedlevel.

The amount of heat evolved in alkylation reactions isga function of thetype of alkylation reactants, i. e., the heat of alkylation will varywith different reactants, and the temperature rise of the reactionmixture will be a function of the heat of alkylation and the relativeamounts and specific heats of the reactants, acid catalyst, alkylateproduct, and any inert hydrocarbons which may be contained in thehydrocarbon feed stocks. The acid catalyst has a relatively highspecific heat and when employed in volumeratios of at least three to oneis capable of absorbing the exothermic heat of reaction and preventingan undesirably large increase in the temperature of the reactionmixture. The acid catalyst separated from the reactor eilluent andrecycled to the reactor will contain the heat absorbed from thealkylation reaction minus or plus, of course, that heat which may beconducted to or taken from the atmosphere through the walls of thereactor, separator, pipe 1ines,-etc., and the cumulative effect of theheat contained in the recycle acid increasing the temperature of thereaction mixture with repeated recycling is avoided by cooling therecycle acid, or a portion of the recycle acid, to a sumciently lowtemperature.

The efiect of acid catalyst-hydrocarbon ratio on the rise of temperatureof the reaction mixture is shown in the following table. The data wereobtained by alkylating isobutane feed stock with butene feed stock in asingle-pass reactor and employing varying volume ratios oi. hydrofluoricacid to total hydrocarbons. The isobutane and butene feed stock combinedanalyzed propane, 60% isobutane, 12% butene. 21% normal butane, and 2%pentane by volume.

m a Woods Acid to ma Hydrocarbons Tm nor. are 3tol 1a1 4.1m 1.2 Dtole0l9tol 24 temperature of the reaction mixture may be continuouslymaintained.

The use of hydrofluoric acid-hydrocarbon ratios of at least three to-oneresults not only in minimizing localized and general overheating of thereaction mixture by absorbing the exothermic heat oi reaction but hasthe additional efiect of improving the quality of the alkylate productthrough the catalytic eflect oi the large volumes of acid catalyst.Heretoiore,

'isoparaflin-olefln alkylations, particularly isobutane-butenealkylation, have been carried out by employing hydrofluoricacid-hydrocarbon ratios of about one to one or slightly higher, 1. e.,the volume 0! hydrofluoric acid employed, including the recycle acid,has been equal to or slightly greater than the volume of isobutane andbutene feed stock, including any normal parafflns or other inerthydrocarbons contained therein, plus the recycled isobutane. It

has been recently discovered, as disclosed in my co-pending applicationwith Urban H. Wagner and Carl S. Kuhn, Jr., Serial No. 561,888, filedNovember 4, 1944, that significant increases in the octane numbers ofthe alkylate products are obtained by employing hydrofluoric acid-hydrocarbon ratios of at least three to one. As the copending applicationdiscloses, it appears that the controlling factor in isoparaifln-olefinalkylation producing high yields of branched chain compounds having highoctane numbers, for example, high yields of 2,2,4-trimethyl pentane(iso-octane) by the alkylation of isobutane with butenes, is a lowconcentration of olefin dissolved in the acid phase of the reactionmixture or, which is the same thing since isoparafllns are only slightlysoluble in the .acid phase, a. high ratio of dissolved lsoparaflin toolefin. As the co-pending application further discloses, eflectively lowconcentrations of dissolved olefin or high ratios of dissolvedisoparaflln to olefln are obtained by employing volume ratios of acidcatalyst to total hydrocarbons fed to the alkylation reactor of at leastthree to one. Thus, the use of acid to hydrocarbon ratios of at leastthree 4 to one is an important feature or the present invention whenemploying hydrofluoric acid as the catalytic agent in the alkylation 0!isoparaflina from the standpoint of obtaining the catalytic effect ofthe high ratios of acid to bydrocarbons on the quality or the productand the eflect of minimizing localized and general rise in temperatureor the reaction mixture.

While satisfactory results may be obtained by employing ratios oi acidto hydrocarbon or at least three to one, it is desirable to employhigher ratios, as, for example, ratios of 10 to 1 to to 1. Evenextremely high ratios, such as ratios of 200 to l and higher, may beemployed since both the catalytic effect and the temperature controllingeflect oi the acid increases with increasing acid ratios,

The entire amount of acid being fed to the reactor may be cooled or onlya portion or the acid may be cooled. For example, the recycle acid aloneor only a portion of the recycle acid may be cooled, or the entireamount or only a portion or the recycle acid plus fresh or regeneratedmake up acid may be cooled. The extent to which the acid is to be cooledwill depend upon the temperature rise 01' the reaction mixture and theamount of acid being cooled. Thus, where the entire amount of acid iscooled the extent oi cooling will be less than where only a portion ofthe acid is cooled. Preferably, the entire amount of acid is cooled orthe cooled portion thoroughly premixed with the rest 01' the acid goingto the reactor in order to avoid localized under-cooling at the inletportion of the reactor. The extent of cooling required will vary foreach particular case and can be determinedby those skilled in the art byactual operation or by calculation.

The essential feature of single pass reactors is a substantially steadyforward flow of the reaction mixture from the inlet to the outlet of thereactor and the process of the invention is applicable to any type ofreactor fulfilling this condition. The reactor maybe a straight chamheror may be a curved tubular reactor. It desired, the reactormay beprovided with baiiies or other flow distributing means of such nature asto increase the turbulence of the reaction mixture without substantialinterference with its predominantly forward flow through the reactor.

The process of the invention may be employed for the alkylation ofisobutane with ethylene,

'. propylene, butenes, pentenes, etc., and the alkylation of isopentanewith these same oleflns. However, the process of the invention may beemployed in connection with any type of alkylation. The feed stocks mayconsist entirely of the pure reactants such as pure isoparaflln and pureolefin, or mixtures of pure isoparafllns and pure olefins, or maycontain normal paraflins or other inert hydrocarbons. Refinerybutane-butane mixtures obtained, for example, by the fractionation ofgas mixtures from cracking operations or by the partial dehydrogenationof butane fractions obtained from natural gas or from stabilization ofnatural or straight run naphthas and containing normal butane andhydrocarbons heavier and lighter than 4-carbon atom hydrocarbons may beemployed in isobutane-butene alkylation. However, it is desirable tocarry out the alkylation reaction with feed stocks containing minimumamounts of inert hydrocarbons.

Conventional alkylation conditions with respect to temperature,pressure-and isoparafllnolefln ratio may be employed. For example, the

alkylation of isobutane with butenes may be carried out at temperaturesbetweerr about F. and 150 F; at pressures at least sufllciently high tokeep the hydrocarbons and hydrofluoric acid in the liquid phase and withisobutane-butene ratios of between 2 to 1 and 15 to 1, preferablybetween about 6 to 1 and to 1. Ratios of isobutane to butenes of atleast 2 to l'are essential since lower ratios tend to causepolymerization of the butenes with resultant decrease. in yield of thealkylate product and/or excessive reaction between the butenes andtheprimary alkylate product because of the relatively low ratios ofisobutane to alkylate product in the reaction mixture. The hydrofluoricacid may be anhydrous hydrofluoric acid or may have a titratable acidityas low as 70% by weight. Following alkylation, the reaction products maybe treated in known manner for separation and reuse of hydrogen fluoridecatalyst, separation and recycling of unreacted isoparafiin and recoveryand purification oi alkylate product. I

The accompanying drawing is a flowsheet illustrating one mode ofcarrying out the-process of the invention in connection with thealkylation of isobutane with butene.

Referring now to the drawing, isobutane in the liquid state enters thesystem through line i0 provided with a suitable control valve H and isadmixed in line I 2 provided with a suitable control valve l4 withrecycle isobutane obtained in the manner hereinafter described. Theisobutane is admixed with liquid butene feed entering the system throughline l5 provided with a suitable control valve i6, and the combinedfeeds passed to alkylation reactor IT. The volume of isobutane fed tothe alkylation reactor is regulated by means of flow controller i8operating valves I! and I4 and activated by flow responsive means [9,and the volume of butene is regulated by means of flow controller 20operating valve I 6 and activated by flow responsive means 2|.

Fresh and/or regenerated liquid hydrofluoric acid enters the systemthrough line 22 provided with a suitable control valve 24 and is admixedin line 25, also provided with a suitable control valve 26, with recyclehydrofluoric acid obtained in the manner hereinafter described. Thevolume of hydrofluoric acid is regulated by means of flow controller 21operating valves 24 and 2B and activated by flow responsive means 29.The acid in line 25 passes through acid cooler 30 where it is cooled tothe desired temperature and'then passes to reactor i i. The mixedhydrofluoric acid and hydrocarbon feeds pass through the reactor and arewithdrawn through line 3i and passed to separator 32 for gravityseparation of the acid from the hydrocarbons. Recycle acid catalyst iswithdrawn from the lower portion of separator 32 and returned throughline 25 to the reactor, fresh and/or regenerated acid entering throughline 22 as necessary. Line 34 provided with valve 35 is connected to theline 25 for continuous or intermittent removal of a portion of therecycle acid for regeneration. After regeneration, the acid may bereturned to the system through line 22.

The hydrocarbon phase from the separator 32 is taken overhead throughline 36 and sent to hydrofluoric acid stripping column 31 where a majorportion of dissolved and suspended hydrofluoric acid carried over in thehydrocarbon phase is vaporized and returned after condensation inanalyzed as follows:

condenser 39 to the separator 32 through line 40 4 provided with valve4|. The bottoms from stripper 31 are passed through line 42 todeisobutanizer 44 for removal of isobutane. Residual traces ofhydrofluoric acid and organic fluoride contained in the bottoms fromstripper 3'! may be removed by chemical treatment, as with bauxite,prior to introduction of the hydrocarbons in deisobutanizer 44. Theisobutane is removed as overhead through line 45 and passed to condenser48 maintained under such conditions of temperature and pressure that theisobutane condenses while any lighter hydrocarbons which may have formedduring the alkylation reaction or which may have been contained in thehydrocarbon feed remain in the gaseous state. The gases pass out of thecondenser through line 41 provided with valve 49 and the liquidisobutane is recycled through line l2 to the alkylation reactor 11. Thebottoms from deisobutanizer 44 are passed through line 50 to debutanizer5| where normal butane formed during the reaction or which may have beencontained in the feed hydrocarbons is removed as overhead through line52. If desired, the normal butane from line 52. may be isomerized toisobutane and recycled to the reactor H. The debutanizer bottoms arepassed through line 54 to iractionator '55 where the alkylate product isseparated into aviation alkylate and heavy alkylate. The heavy alkylateis removed as hottoms through line 55 and the aviation alkylate isremoved as overhead through line 51 and condensed in condenser 59.

The following examples are illustrative of the results obtainable by theprocess of the invention. In these examples, isobutane feed stock wasalkylated with butene feed stock employing hydrofluoric acid as thecatalyst. The feed stocks Volume Per Cent Hydrocarbon Examplel Propaneand Propylene isobutane";

Pentane, Pentenes, and heavier and were used in proportions to give theisobutane-butene ratios indicated in the-table below. The reaction wascarried out in a single-pass reactor comprising a section of straightpipe one inch in diameter and twenty-feet long. The reactor eiliuent wassent to a separator where the hydrofluoric acid was allowed to settlefrom the hydrocarbon phase and the separated acid was recycled to thereactor. The entire amount of recycle acid plus the make-up acid wascooled before entering the reactor. The hydrocarbon phase was strippedof dissolved hydrofluoric acid and chemically treated for removal of anyremaining hydrofluoric acid and was then deisobutanized, the isobutanebeing recycled to the reactor. Thereafter, the hydrocarbon phase wasfractionated for removal of normal butane and lighter hydrocarbons. Theresulting product was regarded as the total alkylate product. The totalalkylate product was then fractionated into heavy alkylate and aviationalkylate, the aviation al- Example 2 Table Example Number.-. l 2

l operamn-oleiin Ratio 1: Volume 6. 9 6. 4 H droflilioric Acid-Totalfiydrocarbon Ratio 39 to l 190 to 1 V ume Titl ltflblb Acidity oiHydrofluOrio Acid,

Weight Per cent 89. 6 89. 3 Residence Time of Reactants in Reactor,

Seconds l 3 Mrs Velocity of Reactants in Reactor, Pounds r Square Footper Second 79 m In at Temperature of Reactants, F 90 00 OutletTemperature of ctauts, F 9i. 1 90. 2 Yield oi Total Alkylate on Basis ofButenes Consumed, Volume Per cent 179 184 Yield of Aviation Alkylate onBasis of Butenes Consumed, Volume Per cent 166 174 F-& Octane Number ofAviation Alkylatc:

Clear 1 90. 8 91. 2 F-i Octane Number of Aviation Alkylate S-l-cc. oiTetraetbyl Lead per Gallon 2. (B 2. 71

lead r llon.

(T I 3 and F-4 octane numbers were determined by the standard AviationFuel Division motor methods.)

It will be seen from the above table that high yields of high octanenumber alkylate product are obtained by the process of the invention.

Having thus described my invention, it is to be understood that suchdescription has been given by way of illustration and example only andnot by way of limitation, reference being had for the latter purpose tothe appended claims.

I claim:

1. In an alkylation process of the type wherein a liquid isoparaffin, aliquid olefin, and hydrofluoric acid catalyst are fed into the inlet ofa single-pass reaction zone wherein substantially forward flow ofreaction mixture is maintained, the reaction mixture including alkylateproduct,

'isoparaflin, hydrofluoric acid, and any unreacted olefin is withdrawnfrom the outlet of said reaction zone and sent to a separation zone forseparation into a hydrocarbon 'phase and an acid phase, and the acidphase recycled to the inlet of said reaction zone for admixture withfresh isoparaflin and olefin, the improvement in controlling thetemperature of the reaction mixture in the reaction zone which comprisesregulating the volume of hydrofluoric acid fed to said reaction zoneincluding that recycled from said separation zone to the volume of totalhydrocarbons fed to said reaction zone such that the volume ofhydrofluoric acid in said reaction zone is at least ten times as greatas the total volume of hydrocarbons in said reaction zone and cooling byindirect heat exchange at least a portion of the hydrofluoric acid to atemperature such that the average temperature of the entire portion ofhydrofluoricacid entering said reaction zone is sufliciently below themaximum temperature desired therein that substantially the entire heatof reaction will be taken up by the reaction mixture without raising thetemperature thereof in excess of the predetermined maximum valuedesired. 2. In an alkylation process of the type wherein a liquidisoparaflin, a liquid olefin, and hydrofluoric acid catalyst are fedinto the inlet of a single-pass reaction zone wherein substantiallyforward flow of reaction mixture is maintained, the reaction mixtureincluding alkylate product, isoparaflin, hydrofluoric acid, and anyunreacted olefin is withdrawn from the outlet of said reaction zone andsent to a separation zone for separation into ahydrocarbon phase and anacid phase, and the acid phase recycled to the inlet' of said reactionzone for admixture with fresh isoparaflin and olefin, the improvement incontrolllng the'temperature of the reaction mixture in the reaction zonewhich comprises regulating the volume of hydrofluoric acid fed to saidreaction zone including that recycled from said separation zone to thevolume of-total hydrocarbons fed to said reaction zone such that thevolume of hydrofluoric acid in said reaction zone is between ten andfifty times as great as the total volume of hydrocarbons in saidreaction zone and cooling by indirect heat exchange at least a portionof the hydrofluoric acid to a temperature such that the averagetemperature of the entire portion of the hydrofluoric acid entering saidreaction zone is sufllciently below the maximum temperature desiredtherein that substantially the entire heat of reaction will be taken upby the reaction mixture without raising the temperature thereof inexcess of the predetermined maximum value desired.

3. In an alkylation process of the type wherein a liquid isopara'filn, aliquid olefln, and hydrofluoric acid catalyst are fed into the inlet ofa. single-pass reaction zone wherein substantially forward fiow ofreaction mixture is maintained, the reaction mixture including alkylateproduct, isoparamn, hydrofluoric acid, and any unreacted olefin iswithdrawn from the outlet of said reaction zone and sent to a separationzone for separation into a hydrocarbon phase and an acid phase, and theacid phase recycled to the inlet of said reaction zone for admixturewith fresh isoparafiin and olefin, the improvement in controlling thetemperature of the reaction mixture in the reaction zone which comprisesregulating the volume of hydrofluoric acid fed to said reaction zoneincluding that recycled from said separation zone to the volume of totalhydrocarbons fed to said reaction zone such that the volume ofhydrofluoric acid in said reaction zone is between ten and fifty timesas great as the total volume of hydrocarbons in said reaction zone andcooling by indirect heat exchange the entire portion of hydrofluoricacid entering said reaction zone to maintain the inlet and outlettemperatures of the reaction mixture at predetermined values.

4. In an alkylation process of the type wherein a liquid isoparaflin, aliquid olefin, and hydrofluoric acid catalyst are fed into the inlet ofa single-pass reaction zone wherein substantially tion zone includingthat recycled from said separation zone to the volume of totalhydrocarbons fed to said reaction zone such that the volume ofhydrofluoric acid in said reaction zone is 200 times as great as thetotal volume of hydrocarbons in said reaction zone and cooling byindirect heat exchange the entire portion of hydrofluoric acid enteringsaid reaction zone to maintain the inlet and outlet temperatures of thereaction mixture at predetermined values.

JOE E. PENICK.

(References 611 following page) REFERENCES CITED The followingreferences are of record in' the file of this patent:

UNITED STATES PATENTS Number Name Date Gibson Apr. 25,- 1944 Frey Dec.7, 1943 Grosse et al July 27, 1943 10 Grosse et al Dec. 30, 1941 Tayloret a1 Feb. 8, 1944 Bowles Nov. 23, 1943 Number Number OTHER REFERENCESGerhold et al., Nat. Pet. News, Tech. Sec., March 1, 1944, pages R-146,R-148, R-150, R-151, R-154 and 55-155. Patent Offlce Library.

